Young Thomas, Andersen Hans C
Department of Chemistry, Stanford University, Stanford, California 94305, USA.
J Phys Chem B. 2005 Feb 24;109(7):2985-94. doi: 10.1021/jp0454927.
We used molecular dynamics computer simulations to test an approximate scaling principle that conjectures that two equilibrium atomic liquids have very similar dynamical properties if they have the same density and similar static pair correlation functions when the length scales of the two liquids are adjusted appropriately, even if they have different interatomic potentials and different temperatures. The simulations were performed on two types of model atomic liquids at various temperatures at the same density. In the first type, the interatomic potential is the Lennard-Jones potential (LJ). In the second type, the interatomic potential is the repulsive part of the Lennard-Jones potential (RLJ). We identified pairs of systems that have very similar pair correlation functions despite the fact that they had different potentials. Each pair consisted of an LJ liquid at a specific temperature and a corresponding RLJ liquid at a lower temperature. We compared various time correlation functions and transport coefficients of the two systems in each pair. Many dynamical properties are very similar in each pair, in accordance with the approximate scaling principle, whereas others are significantly different. The results indicate that certain dynamical properties are very insensitive to large changes in the interatomic potential that leave the pair correlation function largely unchanged, whereas other dynamical properties are much more sensitive to such changes in the potential. The transport coefficients for diffusion and viscosity are among the dynamical properties that are insensitive to such changes in the potential, and this may be part of the reason transport properties of many fluids have been calculated or rationalized in terms of a simple hard sphere model of liquids.
我们使用分子动力学计算机模拟来检验一种近似标度原理，该原理推测，如果两种平衡原子液体在适当调整其长度尺度后具有相同的密度和相似的静态对关联函数，那么它们具有非常相似的动力学性质，即使它们具有不同的原子间势和不同的温度。在相同密度下，对两种类型的模型原子液体在不同温度下进行了模拟。第一种类型中，原子间势是 Lennard-Jones 势（LJ）。第二种类型中，原子间势是 Lennard-Jones 势的排斥部分（RLJ）。我们识别出了尽管具有不同势但具有非常相似对关联函数的系统对。每一对由特定温度下的一种 LJ 液体和较低温度下的一种相应 RLJ 液体组成。我们比较了每一对中两个系统的各种时间关联函数和输运系数。根据近似标度原理，每一对中的许多动力学性质非常相似，而其他一些则有显著差异。结果表明，某些动力学性质对原子间势的大幅变化非常不敏感，这些变化使对关联函数基本保持不变，而其他动力学性质对势的这种变化则更为敏感。扩散和粘度的输运系数属于对势的这种变化不敏感的动力学性质，这可能是许多流体的输运性质已根据简单的液体硬球模型进行计算或合理化的部分原因。
